json resource: Add handling for command: error

This provides the user with messages if `json(command: 'command_that_errors')`
exits non-zero and/or has STDERR.

Without this the resource will report "No output from command" when really the
output is contained in STDERR.

Signed-off-by: Jerry Aldrich <jerryaldrichiii@gmail.com>

lib/inspec/resources/json.rb

@@ -93,10 +93,25 @@ module Inspec::Resources
     end
 
     def load_raw_from_command(command)
-      command_output = inspec.command(command).stdout
-      raise Inspec::Exceptions::ResourceSkipped, "No output from command: #{command}" if command_output.nil? || command_output.empty?
+      command_result = inspec.command(command)
 
-      command_output
+      case command_result.exit_status
+      when 0
+
+        # TODO: Handle case where command exits 0 but STDERR is found.
+
+        if command_result.stdout.empty?
+          raise Inspec::Exceptions::ResourceSkipped, "No output from command: #{command}"
+        end
+      else
+        if command_result.stderr.empty?
+          raise Inspec::Exceptions::ResourceFailed, "Command exited non-zero but STDERR was empty"
+        else
+          raise Inspec::Exceptions::ResourceFailed, "Command exited non-zero. Error:\n #{command_result.stderr}"
+        end
+      end
+
+      command_result.stdout
     end
 
     # for resources the subclass JsonConfig, this allows specification of the resource

test/unit/resources/json_test.rb

@@ -86,7 +86,7 @@ describe "Inspec::Resources::JSON" do
     end
   end
 
-  describe "#load_raw_from_file" do
+  describe "#load_raw_from_command" do
     let(:cmd_str)  { "curl localhost" }
     let(:resource) { Inspec::Resources::JsonConfig.allocate }
     let(:inspec)   { mock }
@@ -97,18 +97,27 @@ describe "Inspec::Resources::JSON" do
       inspec.expects(:command).with(cmd_str).returns(command)
     end
 
-    it "raises an exception if command stdout is nil" do
-      command.expects(:stdout).returns(nil)
-      proc { resource.send(:load_raw_from_command, cmd_str) }.must_raise Inspec::Exceptions::ResourceSkipped
-    end
-
-    it "raises an exception if command stdout is empty" do
+    it "skips the resource if command exits zero and stdout is empty" do
+      command.expects(:exit_status).returns(0)
       command.expects(:stdout).returns("")
       proc { resource.send(:load_raw_from_command, cmd_str) }.must_raise Inspec::Exceptions::ResourceSkipped
     end
 
+    it "fails the resource if the command exits non-zero and stderr is not empty" do
+      command.expects(:exit_status).returns(1)
+      command.expects(:stderr).returns("This is a fake stderr message").twice
+      proc { resource.send(:load_raw_from_command, cmd_str) }.must_raise Inspec::Exceptions::ResourceFailed
+    end
+
+    it "fails the resource if the command exits non-zero and stderr is empty" do
+      command.expects(:exit_status).returns(1)
+      command.expects(:stderr).returns("")
+      proc { resource.send(:load_raw_from_command, cmd_str) }.must_raise Inspec::Exceptions::ResourceFailed
+    end
+
     it "returns the command output" do
-      command.expects(:stdout).returns("json goes here")
+      command.expects(:exit_status).returns(0)
+      command.expects(:stdout).returns("json goes here").twice
       resource.send(:load_raw_from_command, cmd_str).must_equal "json goes here"
     end
   end